The proposed research into aspects of otoconial seeding, growth, and dissolution in experimental animals is aimed at providing a better understanding of human disease- and age-related otoconial loss. Developing inner ears of rat fetuses are being studied by transmission electron microscopy to learn sites and fetal age(s) of otoconial seeding. Scanning electron microscopy of mouse, rat and human otoconia is being carried out in an attempt to identify an easily available experimental model for human, age-related progressive saccular otoconial degeneration. Biochemical analysis of the organic otoconial fraction for identification of amino acids and numbers and molecular weights of proteins present is a primary goal. Radioautography can then be utilized to uncover the metabolic pathways taken by certain amino acids incorporated into the proteins of the otolithic membranes and otoconia, and to ascertain changes in composition or rate of turnover of the proteins in old versus young animals. Distribution of specific enzyme-sensitive organic components in the otoconia will be studied histochemically. Results are expected to shed more light on the possible roles of the organic otoconial fraction in the processes of crystal seeding, growth, maintenance and dissolution, and will be relevant to understanding disease- and age-related vestibular dysfunction, including cupulolithiasis, in man.